Retention systems are used to retain internal components (i.e. adapter cards) of an electronic device, such as a workstation computer. A computer has adapter cards of various sizes and weights, which customers can modify to add/change functions of the computer (e.g. by way of adding or swapping adapter cards). In general, these cards (generally referred to as Industry Standard Architecture (ISA) or Peripheral Component Interconnect (PCI) adapter cards) have traditionally been small and rather lightweight and thus were easily retained (physically) within the computer, even during shipping. As such, computer manufactures did not have particular difficulties in shipping computers containing various adapter cards, as these lightweight cards tended to stay in place.
In the past, various retention systems have been employed. The cards have been retained with screws. The longer cards were retained both at the front and the rear using a card guide in the front, sometimes a latching mechanism, sometimes not, and a screw at the rear of the chassis. In some computers, there was a screw along the back wall that was removed, and then a user could pop the card out. In newer computers, rather than use a screw, some sort of retaining mechanism along the back wall is used.
The trend in the industry has been to add tool-less features to the mechanical retention systems to make it easier for customers to remove, replace or install adapter cards of their choice. Additionally, the trend in card size has been towards larger, heavier adapter cards. Some cards are half height (e.g. a network card) and consequently are lightweight. Increasingly though, some cards are quite heavy (e.g. two pounds (2 lbs.)). Cards that are larger and heavier can be full height and/or full length and/or double wide. In fact, some cards have their own cooling schemes, e.g. heat sinks, etc., which further increase the weigh of the overall arrangements.
Accordingly, manufacturers have run in to trouble when shipping computers with these larger and consequently heavier cards. A light card is generally not an issue in terms of retaining it in the connector on the motherboard, snuggly up against the chassis. However, the heavier a card gets, the larger its inertia is. Thus, when it comes to shipping a computer, getting the computer to the customer in working condition is sometimes difficult, as the heavier cards have a tendency to disconnect during shipping and can even cause damage to other components of the computer.
Manufacturers attempt to anticipate difficulties in shipping computers, such as drops and vibrations. A number of different means have been employed to help ensure that computers arrive to customers in working condition. One is the carton and the foam that are used to absorb shock energy encountered during shipping inside the carton. This approach, however, does not address the difficulty of keeping the ever larger and heavier adapter cards firmly connected to the motherboard during shipping, avoiding damage to the computer.
When a computer is dropped during shipping, the consequences can be severe when the computer contains heavy adapter cards. In this case of a drop, the computer (and any cards therein) is going to accelerate towards the ground, having inertia, which has to be stopped through deceleration. Of course, the stop comes when the computer hits something (e.g. the ground), abruptly decelerating the computer, but not necessarily the card(s) contained therein. The cards also need to decelerate, but tend to continue along their path and damage (e.g. deform or warp) a computer component (e.g. a rail of the computer) before coming to rest. As a rough estimate, the force (expressed in pounds exerted on an adjacent computer component) required to stop a heavy card (e.g. a card which weighs approximately 2 lbs.) in such a drop to the ground is approximately 200 lbs. Thus, manufacturers have to somehow stop the heavy card (e.g. a graphics card) from moving the retention assembly, disengaging from its card connector, or otherwise coming loose and becoming non-functional, potentially damaging the computer by warping or deforming the computer chassis.
Accordingly, a need has arisen for improved tool-less retention systems that adequately retain and decelerate the heavy adapter cards within a computer.